docs: def read_metrics(self, els_client = None):
          """Reads the bibliographic metrics for this author from api.elsevier.com
               and updates self.data with them. Returns True if successful; else,
               False."""
          try:
              api_response = els_client.exec_request(self.uri + "?field=document-count,cited-by-count,citation-count,h-index,dc:identifier")
              data = api_response[self.__payload_type][0]
              if not self.data:
                  self._data = dict()
                  self._data['coredata'] = dict()
              self._data['coredata']['dc:identifier'] = data['coredata']['dc:identifier']
              self._data['coredata']['citation-count'] = int(data['coredata']['citation-count'])
              self._data['coredata']['cited-by-count'] = int(data['coredata']['citation-count'])
              self._data['coredata']['document-count'] = int(data['coredata']['document-count'])
              self._data['h-index'] = int(data['h-index'])
              logger.info('Added/updated author metrics')
          except (requests.HTTPError, requests.RequestException) as e:
              logger.warning(e.args)
              return False
          return True